It is known that amplifier circuits can be used in conjunction with sampling circuits to acquire and hold a signal, and to apply gain to it. Such circuits are subject to noise, and it is desirable to reduce the noise power that is sampled. Such amplifier and sampling circuit combinations may also be used to form a difference between two signals. Such amplifiers may be provided in analog to digital converters (ADC) to amplify a residue that is passed from one stage of a pipelined ADC to a subsequent stage.